Piston construction



* Dec.' 3; 1946. w, A, LEDwlTH 2,411,886

PISTON CONSTRUCTION. Filed Jjan. 28, 1944 3 Sheets-Sheet 1 -...Uhm

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*PISToN'coNsTRUcTIoN Dec. 3, 1946.

Filed Jan. 28, 1944 5 Sheets-Sheet 2 loo - Dec. 3, 1946. w. A. LEDwrrH2,411,886

PISTON CONSTRUCTION Filed Jan. 28, 194:14;- 5 Sheets-Sheet 3 /lL/QETORwww .ATTORNEY atente ce 3, 1946 I rrs'roN ooNs'rnUo'rloN Walter A.Lcdwlth,

United Aircraft Corporation,

Hartford, Conn., assigner to East Hartford,

Conn., a corporation of Delaware Application January 28, 1944, SerialNo. 520g063 I 14 Claims.

1 This invention relates to a piston construction particularly adaptedfor a free-piston 'engineand-compressor unit.

Since the rate of reciprocation of the piston assembly in these -unitsis partly dependent upon` the weight of the piston assembly, high-speedunits require extremely light weight pistons. A feature of thisinvention is a piston assembly which not only has the desired lightweight but which is strong enough to withstand the stresses on the partsof the piston. These piston assemblies generally include an enginepiston and an attached compressor piston with, in some cases, anattached sleeve forming a part of the air spring. Another feature of theinvention is an arrangement for connecting these parts into an integralstructure.

The engine piston of these units may be internally cooled to control theoperating temperature. A feature of this invention is the arrangement oithe piston assembly to provide for circulation of cooling fiuid throughthe engine piston and theadmission of cooling iluid to the piston. Thisarrangement may include an in= ner cup within the engine piston forkeeping the fluid in contact with the inner wall of the piston or tominimize the volume of cooling fluid in the piston.

Other objects and advantages will be apparent from the specification andclaims and from the accompanying drawings which illustrate anembodir'nent of the invention.

Fig. 1 is a sectional view and-compressor unit.

`Fig. 2 is a sectional view through one piston assembly on a largerscale.

Fig. 3 is a sectional view on line 3 3 oi Fig. 2. The unit shownincludes an engine cylinder l@ having reciprocating pistons l2 and It towhich compressor pistons i6 and I8 in cylinders 2G and 22 are integrallyconnected. Sleeves 24 and 2t attached to the compressor pistons completethe reciprocating piston assemblies. The sleeves in combination withstationary pistons 28 and Sii form air spring cylinders. The pistonassemblies are through the enginemoved apart by the burning of vfuelinjectedfinto engine cylin- 32. A11-.compressed in thc `air springcylinders on the power stroke returns dei= it as by a pump the pistonassemblies. The assemblies are alwaysmaintained at equal distances fromthe center of the enginecylinder by a linkage, vwhich may include racks34 on the compressor pistons meshing with a pinion 3B.

Intake manifold 38 conducts ain to intake valves 40 through which airalternately enters opv posite ends of the compressor cylinders. The

.which a cup 12 air leaves the cylinders through discharge valves 42,also at opposite ends of the compressor cylinders and passes throughscavenge manifold 44 and through ports 48 and 48 which compressed 'areuncovered .by pistons I2 and i4 at the end thereby permitting air to beblown through the engine cylinder and exhaust of the power stroke,

ports 50 and 52 into exhaust manifold 54.

The piston assembly shown in Fig. 2 includes a base 58 to which the lairspring sleeve 26 is attached as by cooperating threads 58 on sleeve andbase. Base 56 has an integral disc 60 forming one side surface of thecompressor piston I8. A cooperating disc 82 is fastened to disc 6B bybolts 84 to form the other side wall ci the compressor pis'- ton. Disc60 has a rim 88 Within which disc 82 is iitted, this rim having a groove68 for one or more piston rings..

Base 56 has a projecting hub 10 to the end o! is attached as bycooperating threads 14, This cup is positioned within and spaced fromthe hollow shell 18 which lis held on the hubby interengagina threads 18on hub and The end of shell 18, which is adiacent the compressor piston.clamps the edge of disc 62 which has a central opening 88 through whichhub 10 extends. Discs 60 and 62 may have intervengaging shear serrations82 on bosses 84 and ribs 88 to resist bending of the piston.

Sleeves 28, cup 12, and shell 18 may all be shrink tits on the base tohold the parts on assembled relations and to form a permanent as sembly.The space 88 between cup 12 and shell 'I6 may be used for circulatingcoolant for the enginepiston. A tube Sii extending centrally from base66 to the end of the cup is held in the base by a hollow bolt 92 and admts coolant into space 88. Passage 94 in base Se a d integral disc 88orovides iiuid connection from tube to one hollow rack 34 into whichfluid is pumped and through which coolant rea-chesthe inside of shell18;

-Base 5B has intersecting passages et and 98, Fig. 3. extending from agroove Ill Fig. 2. in the hub 10 to the other hollow rack 34. fordischarge shell.

s of fluid from space 88 through the rack. Space 8a is connected withgroovel lill! by small passages |02, Fig. 2' in hub 10. All the fluidpassages are in the base and integral hub. and may be formed before theparts are assembled.

It is to be understood that the invention is not .limited to thespecific trated and described, but may be used in other embodimentherein illus-v v ways without departure from its spirit as dened by thefollowing claims.

I claim:

1. A piston construction including a compressor piston comprisingopposed discs and an engine piston attached to one of saiddiscs andclamping the discs together.

2. A piston construction including a compressor piston comprisingopposed discs, andX an engine piston threaded on one of said discs, andclamping the discs together.

, 3. A piston construction including a compressor piston comprisingopposed discs, one of which has a hub extending through the other disc,and an engine piston threaded on said huh and clamping said other disc.

4. A piston construction including a compressor a hub extending throughthe other disc, and an engine piston threaded on said hub and clamping'9. A piston construction including opposed discs forming a piston, oneof said discs having ahub extending through the other disc, a secondpiston attached to said hub and clamping said other said other disc,said hub having shoulders against disc, said disc with the hub having athreaded projection on its opposite side on which a sleeve is mounted. Y

10. A pistonconstruction including avhase, a

liner mounted on said base, and a hollow piston mounted on said basearound and out of contact with said liner.

11. A piston construction including a base, a liner mounted on saidbase, a tube extending from vthe outer end of the liner to a passage inthe base, and a hollow piston mounted on said base around and out ofcontact with said liner.

12. A piston yconstruction vincluding opposed discs forming a piston,one of said discs having a hub extending through the other disc, apassage in said hub, a liner mounted on'said hub and having a connectionwith said passage, and a hollow piston mounted on the hub around saidvliner and spaced therefrom to form a cooling space there- `ioetween. v13. A piston construction including opposed discs forming a piston, oneof saiddiscs having 7. A piston construction including opposed discsyspace therebetween, said hub having a passage from said cooling spaceto an opening in one of said discs.

14. A piston construction including opposed .discs forming a piston, oneof said discs having a hub extending through the other disc, a passagevin said hub, a liner mounted onsaid hub and having a connection withsaid passage, and a hollow piston mounted on the hub around said linerand spaced therefrom to form a cooling space therebetween said pistonclamping said discs together.

WALTER A. LEDWITH.

